After it sold for nearly $3 million in cash in 2012, the gorgeous four-story townhouse in one of Brooklyn’s prettiest neighborhoods proceeded to become an eyesore and a nuisance. Renovations dragged on for several years, then stopped. I-beams and cinder blocks cluttered the yard. Windows broke. Neighbors complained that the construction caused their basements to flood. The security alarm would go off in the middle of the night for an hour at a time.

“The speed of the transaction was strange, and then the length of the renovation was strange,” said William Jeanes, a retired city worker who lives a few doors down.

The absentee owners broke a cardinal rule of brownstone Brooklyn: There is a ginkgo tree near the house, and in the fall, ginkgos drop fleshy, rotten-scented fruits. The owners were the only ones on their block who did not sweep their ginkgo fruit off the sidewalk.

Mr. Manafort’s ownership of the property was first brought to the public’s attention in February by a blogger, Katia Kelly, who runs a neighborhood news site called Pardon Me for Asking. One springlike day, she went out to take pictures for a post about a controversial public school expansion. A passer-by saw her with her camera and offered a scoop.

“She said, ‘Guess who lives on my block?’” Ms. Kelly recalled on Tuesday. “With all the celebrities moving into the neighborhood, my first thought was Jay-Z or Beyoncé, or Gwyneth Paltrow – my mind was going gossipy Hollywood instead of swampy Washington.”

Ms. Kelly dug through public records and determined that Mr. Manafort’s companies had borrowed nearly $7 million against the house. “Even with home prices going up tremendously in Carroll Gardens in the past few years,” she wrote, “one could say that the mortgage amount of $6,803,750 exceeds the current value of this house, especially in its current condition.”

Mr. Manafort, who bought the house through a holding company called MC Brooklyn Holdings LLC, never lived there. The broker who sold the house said that Mr. Manafort’s daughter Jess and her husband told her they planned to renovate it and move in.

“They loved the house,” the agent, Lindsay Barrett, said on Tuesday. “We had two cash offers but they got there first.”

The money for the house was coming from Ms. Manafort’s father, Ms. Barrett said, and she said she confirmed that the money existed before the seller accepted the offer. “It passed the sniff test,” she said.

Ms. Barrett said that she and the house’s prior owner, with whom she remains friendly, “sort of lament a little bit” what has transpired. “But you never know, anything can happen when you sell a property. We sold it, the seller was happy and that’s my goal.” She said the seller did not want to speak to the press.

After nearly two idle years, work resumed a few months ago on the house, a 19th-century Italianate home that featured original plaster molding, marble mantels and a Jacuzzi, neighbors said. Mr. Jeanes watched from his backyard as a deck was erected atop the two-story extension in the back, new windows that run almost from floor to ceiling were installed, and another deck went up on the roof.

“They put in a new walkway in front, too,” Mr. Jeanes said — an L-shaped path of neat slates marking off a patch of precisely groomed dirt, unplanted except for a single tree.

The house’s future is unclear. The real estate news site The Real Deal reported on Tuesday that an associate of Mr. Manafort’s was in the process of putting it back on the market for as much as $9 million – a very high price for the neighborhood, but not unheard-of. The associate, Brad Zackson, did not immediately return a call on Wednesday. According to the indictment, if Mr. Manafort does sell the house and is subsequently convicted, prosecutors will go after the proceeds.

If any cash-flow problems loomed, word had not reached the workers who bustled around the house on Tuesday, repainting the stoop, doing wiring and installing wallboard. A man on drywall stilts walked around in a back room, and another worker was up on a scaffold beneath an ornate oval ceiling medallion.

“It’s our first day here,” said an electrician, Remigiusz Dziegiel.

“Big renovation,” said his colleague Pawel Piotrowski. “It’s going to be nice.”

A version of this article appears in print on , on Page A17 of the New York edition with the headline: In Brooklyn, an Eyesore Becomes Evidence. Order Reprints | Today’s Paper | Subscribe